Improve Facility Operation through Commissioning-A Case Study Mingsheng Liu, Ph.D., P. E. University of Nebraska

Outline 1.Facility information 2.Commissioning measures 3.Measured results and conclusions

1. 1 Building and AHUs Information

1.2 Control Systems Information A modern DDC system was installed in 1995 as part of energy retrofit project –Provide remote control on each AHUs, pump, and terminal box –Provide remote monitoring on critical parameters

1.3 AHUs Information All single duct systems are converted into VAV system with modern DDC control All systems have economizers All AHUs reset supply air temperature according to the outside air temperature New control valves and dampers were installed as part of the energy retrofit project in 1995.

1.4 Boiler Plant Information New boilers were installed in 1995 –Boiler HP (8 MMBtu/hr) –Boiler HP (17 MMBtu/hr) –Boiler HP (23 MMBtu/hr)

1.5 Thermal Storage System

1.6 Measured Hourly Electricity Consumption Before Commissioning

1.7 Measured Hourly Gas Consumption Before Commissioning

1.8 Operation Problems and Concern Thermal Storage System: 1,760 kW peak demand in 1997 (expected to be 1,400 kW) Overall retrofit savings: significantly smaller than the projected value EMCS systems: lack of confidence of smooth operation

2.1 Commissioning Measures Energy Management and Control Systems Buildings Thermal storage systems Boiler systems

2.2 Measures for EMCS Systems Point by point check software Verify hardware in the field Optimize/modify control algorithms –Terminal box –AHUs –Chilled water loop –Hot water loop

2.2.1 Example: VAV Fan Speed Control Existing schedule: Modulate the fan speed to keep at least one of the five terminal box damper at 90%.

2.2.2 Real Operation One of the room temperature set point was 72°F. The occupant wanted to be 76°F. She could not change the set point since it was programmed by the EMCS system. –A foot heater is used to make 76°F –The box is open to fight the heater –The fan is speed up to satisfy the box

2.2.3 Solutions

2.3 Measures for Buildings Chilled water loop balance Hot water loop balance Air flow balance Thermostats and terminal box check up Dampers and linkage check up/repair/replace

2.4 Measures for Thermal Storage System Loop differential pressure set point optimization Chiller on/off schedule Tank charge rate optimization Off-peak demand reduction

2.5 Measures for Boilers Decrease steam pressure from 60 psig to 40 psig at night and weekends Use smaller boiler/boilers

3.1 Comparison of Whole Campus Electricity Consumption

3.2 Comparison of Campus Hourly Gas Consumption (ft 3 /hr)

3.3 Comparison of Measured Peak Demand 1785 kW in 1997 (Before commissioning) 1483 kW in 1998 (During commissioning) ???? In 1999 (After commissioning)

3.4 Comparison of Costs and Savings The measured annual energy savings based on paid utility bills: $146,581 –$69,669 for electrical energy –$24,462 for peak demand –$52,670 for gas The total contract amount: $143,000 The project duration: 10 months (3-98 to 12-98)

3.5 Conclusions Look for significant amount of energy savings from commissioning Look for significant operating improvement from commissioning